Reddit mentions of Kurgo Direct To Seatbelt Tether for Dogs | Universal Car Seat Belt for Pets | Adjustable Length Dog Safety Belt | quick & Easy Installation | Carabiner Clip | Compatible with Any Pet Harness (Orange)

Hi, consider using putting him in a harness (secures across chest, not neck) and getting a clip that attaches to the seatbelt. Along these lines.

Or for $13 you can get this and have your dog safely secured in you car.

Then no pups through the windshield!

I use this one with a ruffwear harness. He loves road trips!

We have a seat cover already. We also use a seat belt tether most of the time.

I like the Waterboy idea. I think I'll get one.

We bought this one. It clicks into the seat belt buckle and attaches to the dog's harness with a carabiner rather than a traditional leash clip, which hopefully makes it less likely to break in an accident. It also comes with an adjustable strap, which is useful for us so our little dog has enough give to lie down, but not enough to jump toward the floor and hang himself.

90lbs Doberman owner here. It can be done, it just takes a few dollars, and some practice with your dog.

• You want a sling/hammock. Don't skimp on the price of this. Not saying the one you linked to is bad (I have no idea, really), but cheaping out on the hammock for your car is kinda dumb :)
  

• You can buy door protectors. They are not perfect - my dog manages to sometimes pull them out of window (they sit there with tabs that go between the glass and the rubber seal), but they're better than nothing.
  
• Get a travel harness. Giving your dog just enough freedom to reorient themselves but not enough so that they can cause an accident/damage your backseat/doors is essential. Also, if you get rear-ended, the last thing you want is an un-tethered dog flying towards your windshield.
  
• To work with the above harness (or any harness, really), get a seatbelt clip. It'll let you connect them directly to the seatbelt clip in the back seat, which is great.
  
• Get the interior of your vehicle vacuumed/detailed every month or so. Dogs gonna dog :)

I volunteer at a shelter (and also have my own two pups) and transport dogs all the time. I have an old blanket that I use to cover the backseat of my '11 impreza and I attach this: http://www.amazon.com/Kurgo-Direct-Seat-Belt-Dogs/dp/B00EPKH45U/ref=sr_1_1?s=pet-supplies&ie=UTF8&qid=1408933823&sr=1-1&keywords=kurgo+seat+belt+tether
To the halters of the dogs. It's quick and easy to attach and you can adjust the length of the tether if you want to give them a little wiggle room.